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The ionization source based on glow discharge plasma using ambient air is driven by a pulsed direct-current voltage for soft plasma ionization (SPI). The novelty of this work is that molecular ions [M+13]+ related to the analyte species (M), which may be formed by numerous oxidation, can be dominantly detected as a base peak with little or no fragmentation of them in an air plasma at a pressure of several kPa. The unique ion [M+13]+ was assigned to the oxidation product, [M+O-3H]+, which was confirmed as a deuterated ion [M+O-3D]+ ([M+10]+) by using a deuterated solvent. The ionization reactions were suggested that the product ion [M+O-3H]+ may arise from hydride abstraction reaction of M with O2+•, dehydrogenation reaction of [M-H]+• and subsequently oxidation reaction of [M-3H]+ with O3. n-Alkane mixtures was also measured to evaluate the intermolecular interaction in this system. The limits of detection (LOD) were in the range of 0.126-1.68 ppmv and the relative standard deviation (RSD) for repeatability was approximately 10.0% at the lowest concentration. To our knowledge, this is the first report demonstrating that the spectrum pattern of saturated hydrocarbons could be directly determined without any complicated fragmentation.

This study describes a direct analysis of oxygenated organic compounds, such as ketones, esters and ethers, rapidly and easily using a soft plasma ionization (SPI) source combined with a Q-mass spectrometer. A related molecular ion, [2M+H]+, in which a sample molecule (M) can undergo protonation via water clusters, such as [(H2O)n+H]+ and [N2(H2O)n+H]+, in an ambient air glow discharge plasma, can be dominantly detected as a base peak with little or no fragmentation at a pressure of several kPa. Oxygenated organic compounds with high proton affinity were found to generate their dimers through the hydrogen bonding interaction at higher pressures. A deuterated solvent was used to examine whether or not the adduct ion of analyte was derived from the solvent. The formation of [2M+H]+ strongly depended on the time. A two-dimensional spectrometer was used to obtain the distribution of several excited species and then to confirm the ionization reactions of the analyte in the SPI source. The sample molecule would be readily ionized through Penning-type collisions with excited N2, which causes fragmentation for oxygenated compounds due to the lower pressures (approx. 1.0 kPa) while it is ionized by an attachment with protons from water clusters at higher pressures (several kPa). The SPI source can be a new and powerful tool for soft ionization in direct analysis of volatile organic compounds (VOCs).

The objective of this paper is to suggest a new method for controlling temporal response of the emission signal from a pulsed radio-frequency (RF) glow discharge plasma for optical emission spectrometry. It is a noticeable feature that the emission profile accompanies a transient stage in the pulsed operation, appearing as a pre-peak which sometimes becomes 10–20 times as large as the plateau-stage intensity. Therefore, it is worth studying how the spike-like transient signal can be modified to a smooth response following the square-wave timing signal by using any experimental procedure. For this purpose, a phenomenon regarding self-bias voltage in RF plasma was focused on. The self-bias voltage is induced near the RF-loaded electrode, and then, a bias current can be introduced through an electric circuit including the plasma body by connecting an external electric device with the glow discharge plasma source. The bias current could be also pulsated, while it was synchronized with the pulsed RF plasma. Larger pulses of the bias current could change the characteristics of the plasma for atomic emission spectrometry, extending the size of the RF plasma as well as enhancing the emission intensity, which enabled the plateau stage to become more prominent in the pulsed emission profile. Several experimental parameters, such as an amplitude of the bias current, duty ratios of both the RF power and the bias current, and a phase shift between them, were investigated to obtain a plateau-like transient response of the emission signal. It was found that the phase-shift angle should be regulated between timing pulses of the RF voltage and the bias current.

This study describes an ionization source for mass analysis, consisting of glow discharge plasma driven by a pulsed direct-current voltage for soft plasma ionization, to detect toxic volatile organic compounds (VOCs) rapidly and easily. The novelty of this work is that a molecular adduct ion, in which the parent molecule attaches with an NO + radical, [M + NO] + , can be dominantly detected as a base peak with little or no fragmentation of them in an ambient air plasma at a pressure of several kPa. Use of ambient air as the discharge plasma gas is suitable for practical applications. The higher pressure in an ambient air discharge provided a stable glow discharge plasma, contributing to the soft ionization of organic molecules. Typical mass spectra of VOCs toluene, benzene, o -xylene, chlorobenzene and n -hexane were observed as [M + NO] + adduct ion whose peaks were detected at m / z 122, 108, 136, 142 and 116, respectively. The NO generation was also confirmed by emission bands of NO γ-system. The ionization reactions were suggested, such that NO + radical formed in an ambient air discharge could attach with the analyte molecule.

For thermal recycle by wasted plastics coated around electric cables, ignition and combustion experiments of the pulverized samples were carried out, using two types of electrically heated drop tube furnace, in which the particles are pulsatively fed and continuously fed, respectively. The ignition phenomenon was defined as occurrence of luminous emission from a cloud of the particles fed in the former furnace. The wasted plastics coated around the electric cables mainly make of polyethylene with a little amount of carbon particles. The ignition characteristics of the pulverized plastic samples as well as graphite particles as a reference sample were studied, changing the particle diameters and the furnace wall temperatures. In the electrically heated drop tube furnace with the continuous feeding system, the wall temperature and stoichiometric combustion air ratio were varied to elucidate the fundamental combustion characteristics. As a result, the ignition temperature depended on the particle diameter. The plastics with the particle diameter ranged from 150 to 300 µm could ignite at the lowest furnace temperature. From the continuous combustion tests, CO and lower molecule hydrocarbons like CH4, C2H2 and C2H4 were produced in the upper region of furnace. Finally, all of them gradually burned out.

Oxy-fuel coal combustion has drawn attention as a useful technique to achieve carbon dioxide capture and storage (CCS). It is the technique that enriches CO 2 in exhaust gas by flue gas recirculation with additional pure O 2 , which makes it easy to capture and liquidize CO 2 downstream. However, in the oxy-fuel combustion system, various impurities in the flue gas are brought back to the combustion zone with recirculated flue gas, and more have accumulated in a boiler compared with the air combustion system. NO X formations, in particular, can be affected by nitrogen contents in the raw coal and recirculated multiple NO X compounds, such as NO and N 2 O. Then, in this study, we experimentally estimated the effects of NO and N 2 O recirculation by a drop tube furnace equipment simulating oxy-fuel atmosphere for three coal samples with different nitrogen contents. As a result, contributions of recirculated NO X to NO X emissions were found to be very small in oxy-fuel coal combustion. Instead, nitrogen conversion ratios to NO and N 2 O were governed by the ratio of char-N to fuel-N.

This study describes a measuring system for mass spectrometry, consisting of a glow discharge ionization source for soft plasma ionization and a time-of-flight mass spectrometer, to detect toxic volatile organic compounds rapidly and easily. It is the most important to determine how the complicated fragmentation of such compounds can be suppressed to occur so as to recognize the mass spectra of the volatile organic compounds as their fingerprints. The novelty of this work is that the optimal discharge condition for the soft plasma ionization–time-of-flight mass spectrometer system could be selected, so that the parent mass peak of analyte molecules could be observed both with high sensitivity and with little or no fragmentation of them. Use of air gas at a pressure of 1000 Pa provided the most favorable result for these criteria, whereas, in a previous report, the soft plasma ionization source operating with argon at a pressure of 346 Pa had yielded additional mass peaks of the fragmented species...

Environmental contextPolycyclic aromatic hydrocarbons are carcinogenic environmental contaminants that tend to migrate into the sediments in oceans and seas. Their vertical distribution in sediments from the Seto Inland Sea matched their emission over time, which in turn reflected changes in energy sources and industrial activities in Japan. This study shows that human activities on land directly and significantly influence the concentration of polycyclic aromatic hydrocarbons in sediments. AbstractSeventeen polycyclic aromatic hydrocarbons (PAHs) were identified in sediment cores collected at several locations in the Seto Inland Sea in 2015 and 2016 to understand their spatial distribution and potential emission sources. PAHs were analysed using gas chromatography–mass spectrometry. The age of the sediment cores was analysed using radioisotopic dating techniques to reconstruct historical PAH emissions. The total concentrations of 17 PAHs in the sediment cores of Osaka Bay in 2015 were in the range of 108–2810ng g−1 dry weight (dw) with a mean concentration of 1050ng g−1 dw. The total concentrations of 17 PAHs in sediment cores from the Seto Inland Sea in 2016 were in the range of 52.6–941ng g−1 dw with a mean concentration of 313ng g−1 dw. The spatial distribution of PAHs showed the highest concentration in Osaka Bay and the lowest in Kii Channel in 2016. The horizontal PAH distribution showed a decreasing trend in concentrations from the estuary offshore to Osaka Bay and Aki-Nada. The vertical PAH distribution revealed that levels were higher before the 1980s–1990s, when oil consumption and industrial activities in the Osaka region reached a maximum in the 20th century. The diagnostic ratios of PAHs and a principal component analysis revealed three main emission sources of PAHs, industry, biomass burning and traffic activities.

Counter-flow packed bed gasification was carried out featuring a combination of downdraft and updraft operation modes. A column reactor of inside diameter 102 mm and 1000 mm height was used. Downdraft and updraft air supply were varied while the total air supply was maintained constant. Counter-flow gasification with downdraft air supply at 12 L/min and updraft air at 4 L/min offered optimal conditions, producing syngas with 4.28 MJ/m 3 N LHV and 5.84 g/m 3 N tar content. Under similar operating conditions, cold gas efficiency was about 77% while carbon conversion reached 88%. Increasing the updraft air flow resulted in reduced tar generation and increased carbon conversion, however, the syngas LHV and cold gas efficiency were affected adversely.

Some ash particles in solid fuels adhere on heat exchanger tube surfaces inside coal and/or biomass combustion boilers. The authors have already proposed a surface treatment on tubes, using a thermal spraying technique, to reduce ash deposition. Understanding reduction mechanisms of the ash deposition is necessary to evaluate effects of the surface treatment technique on the reduction of ash deposition. The reduction mechanisms of the ash deposition were elucidated due to physical and chemical aspects, measuring adhesion forces between the ash particles and some alloy specimens of the tube at high temperature under the simulated boiler conditions. As a result, the adhesion force increased with time and depended on both the ash types and the alloy specimens. The thermal spraying of Ni-alloy, in particular, could reduce the adhesion force. Moreover interface reactions between the ash particles and the alloy specimen played an effective role in increasing the adhesion force, alkali metal compounds in the ash samples also related to an increase of the adhesion force. Fe, which was one of the main alloy elements, diffused into the ash deposition layer beyond the interface. This observation result suggested that the interface reactions of the ash particles with the alloy caused an increase of the adhesion force.

Boron behavior during coal combustion was studied experimentally and theoretically. Seven types of coal with different boron concentrations were pyrolyzed or burned, using an electrically heated drop tube furnace. In order to understand the effect of coal type on the boron component of ash, chemical equilibrium calculations were made to determine which boron compounds contributed to forming the boron compounds found in the ash particles. Additionally, XAFS analyses were also carried out to evaluate the results obtained by the chemical equilibrium calculations. Some boron compounds in coal were volatilized, and others remained in the molten coal ash after combustion. Both the chemical equilibrium calculations of the boron compounds under the combustion condition and the boron analysis of the ash particles by the XAFS suggested that the boron compound contained in the ash was mainly B 2 O 3 . The boron compounds were concentrated in the molten slag during combustion. The enrichment of boron into the ash as particles was related to the amount of slag formed. The index, (Base/Acid ratio) × (Ash content), correlates well with the volatilization fraction of boron even in the actual power plants.

It is important to be aware of the particle size distribution and composition of ash in coal combustion for prediction and control of ash deposition behavior, which results in the degradation of boiler performance via fouling and slagging. To elucidate fragmentation and coalescence behavior of mineral particles in a pulverized coal combustion process, char particles during the combustion reaction were sampled and analyzed for their particle size distribution and composition using a drop tube furnace. CCSEM analysis was conducted to identify included and excluded minerals in sampled char particles. Three coal samples having different char structures and ash melting temperatures were tested to estimate the effect of the physical properties of ash on fragmentation and coalescence behaviors of mineral particles. With the progress of combustion, the number of included mineral particles decreased due to their separation from char particles, leading to the increase of the number of excluded mineral particles. The total number of particles decreased with the progress of combustion. Some of particles were agglomerated, and some of them were fused to each other. These behaviors were less obvious for coal which experienced network structure of char particles during its combustion process. On the other hand, minerals in coal characterized by low melting point ash were rounded off during the coal combustion process. Fractions of included mineral were higher at smaller particle sizes, and they decreased with the progress of combustion. Elemental compositions of fused particles in coal characterized by low melting point ash are attributed to that of aluminosilicate.

Lignin and cellulose chemicals were used as artificial biomass components to make-up a simulated biomass. Alkali and Alkaline Earth Metal (AAEM) as well as volatile matter contents in these chemicals were much different from each other. Co-gasification of coal with simulated biomass shows improved conversion characteristics in comparison to the average calculated from separate conversion of coal and simulated biomass. Two conversion synergetic peaks were observed whereby the first peak occurred around 400℃ while the second one occurred above 800℃. Although co-gasification of coal with lignin that has high AAEM content also shows two synergy peaks, the one at higher temperature is dominant. Co-gasification of coal with cellulose shows only a single synergy peak around 400℃ indicating that synergy at low temperature is related with interaction of volatiles. Investigation of morphology changes during gasification of lignin and coal, suggests that their low reactivity is associated with their solid shape maintained even at high temperature.

A time-of-flight mass spectrometry (TOFMS) with a newly laboratory-made sampling cone interface fitted to an atmospheric pressure chemical ionization (APCI) positive ion source was successfully applied to easy, rapid on-line measurements of nanoparticles and components generated during combustion. The mass spectra for smoke from a mosquito coil ranged up to m/z 1202, corresponding to 1.2 nm with the carboneous material density as graphite 2.2 g cm−3. Typical m/z peaks were assigned to such synthetic pyrethroids, as d-allethrin and d-tetramethrin, at m/z 303 and 332, respectively. A specific pattern with a peak-to-peak interval of 74 was recognized in the higher mass range. The interval of 74 was confirmed by measuring with a standard silica solution in a positive ion mode using a conventional APCI interface under the same APCI conditions. The mass spectrum of the silica solution had a pattern with peak interval of 44 which was assigned to SiO. These results indicate that the pattern with an interval of 74 in the mass spectrum of the mosquito coil smoke is sample-derived peak. We assumed that the interval of m/z 74 is assigned to identified as triacetylene (1,3,5-hexatriyne) that is generated during the combustion.

Lithium (Li) ion attachment mass spectrometry (IAMS) is a highly sensitive method for detecting volatile organic compounds (VOCs) without fragmentation in real-time. We have therefore developed a novel IAMS system for direct determination of trace amounts of VOCs by modifying the sampling cone interface. This technique was successfully applied to in situ analysis of human breath. It was shown that the concentrations of acetone in 7 healthy subjects ranged from 0 (not detectable) to 28.5 ppbv (parts per billion by volume) after a 15-hour overnight fast. The detection limit (3σ) is 0.55 ppbv for acetone and the relative standard deviation (RSD) is less than 9.7%. These results demonstrate that the newly developed IAMS system provides simple, rapid, and sensitive measurements of trace amounts of acetone in human breath, and that the system is promising for early diagnosis of diabetes.

The redox potentials of cobalt and iron complexes with ten pyridylazo compounds, E(0)(ML2) (ML(2)(+/0); M: Co(III/II), Fe(III/II); L(-): pyridylazo compounds), have been determined in order to explore the difference in their reversed-phase HPLC behavior. The redox potentials of Co complexes were in the range of -0.62 - 0.03 V, while those of Fe complexes were -0.06 - 0.59 V relative to 0.20 V for ferricinium/ferrocene. The redox potentials of both the Co and Fe complexes were linearly correlated to the basicities of the ligands. The correlation was quantitatively explained by a difference in dependence of the stabilities of M(III) and M(II) complexes on the ligand basicities. The complex of [Co(III)L(2)](+) or [Fe(II)L(2)] with any compound injected in the reversed-phase HPLC system was detected without any change in the composition. When [Co(II)L(2)] was injected, only those complexes having the highest potentials of E(0)(CoL2) congruent with 0.0 V were detected as [Co(II)L(2)], while other complexes having lower potentials gave a peak of [Co(III)L(2)](+). When [Fe(III)L(2)](+) was injected, only complexes having the lowest potentials of E(0)(FeL2) congruent with 0.0 V were detected as [Fe(III)L(2)](+), while others having higher potentials gave a peak of [Fe(II)L(2)].

We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 ± 63, 20 ± 11 and 17 ± 8 [mean ± SD] pg/cm2, respectively., This work was partly supported by the Regional Science Promotion Program, Japan Science and Technology Agency.

Fatty acids (FAs) are biological molecules that are used as major metabolic fuels, and are concerned in important metabolic processes. We have performed a non-invasive and technically rapid and simple method for collecting sweat from humans, followed by GC/MS determination. The sweat was collected from each volunteer (the middle finger) by spraying 70% ethanol aqueous solution (no harmful solvent) into a 1.5-cm 3 plastic vial. Analysis of FAs in sweat showed that the sweat solution contains lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), oleic acid (C18:1), and stearic acid (C18:0). Here, it is demonstrated that FA concentrations for 4 young subjects correlated positively with percent of body fat (r = 0.78) and that the total FA levels for them increased progressively with increasing fasting time when a subject fasted throughout the experiment.

Ash deposition, called fouling, is one of major problems occurring in boiler that incinerates waste products as fuel. Ash deposition layer on heat transfer tube in a boiler causes not only heat transfer inhibition but also corrosion of the surface of heat transfer tube. Compared with pulverized coal combustion boiler, a concern of fouling becomes larger under waste incineration conditions due to their high contents of chlorine compounds. In this study, using ash samples derived from waste incineration processes, ash deposition experiments were carried out in vertical ash deposition furnace with a thermal spraying burner. Ash samples deposited on the tube surface were analyzed for elemental compositions and their distributions, using CCSEM equipped with EDX. A thermal spraying technique was applied to improve the surface properties of heat transfer tubes in boiler for reduction of ash deposition. Ni alloy as a thermal spraying material showed a positive effect to reduce ash deposition even under waste incineration conditions. In addition, to clarify the mechanism of ash deposition, thermal equilibrium analysis was also carried out.